Glues for wood in archery uses (1952) -

7/27/2019 Glues for wood in archery uses (1952) -

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TECHNICAL NOTE number 226UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE

FOREST PRODUCTS LABORATORYmadison 5. Wisconsin revised December 1952

GLUES FOR WOOD IN ARCHERY USES

Glues are used (l)to splice billets for bowstaves, (2) to splice "footings"to arrow shafts, (3) to attach feathers to shafts, (4) to attach facingsand backings of a variety of materials to bows, (5) to lay leather or otherbindings on bow handles, (6) to laminate bows from layers of thin-JKO_odor wood with other materials, and (7) to attach nockff and points to arrowshafts.

Properties of Glues

The woodworking glues that are available to amateur archers may begrouped into several types based on durability of the resultant joint,conditions required in gluing, and cost. The following generalizationsare given for the guidance of archers who do not wish to make a specialstudy of the literature on gluing.(1) No glue will produce joints of maximum strength unless the joint fitsclosely and unless the glue is prepared and used correctly. Directionsfor use are furnished by the manufacturer or supplier. Conditions thatgive best results in gluing with one type of glue may not give best re-sults, or even fair results, with another type of glue.(2) Generally high-grade glues of all principal types of woodworkingglues will give equally high initial, dry joint strength on commonly usedspecies when used under the most favorable conditions for that type ofglue.

(3) Woodworking glues vary widely in their water resistance. In addi-tion, the water resistance of the joint will vary according to the qualitypf the gluing and the effectiveness of the protective coatings.The characteristics of various glues are described in greater detail

in Technical Note Nos. 257, 258.


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(4) Animal glues are characterized by high dry strength, low water re-sistance, and quick gelling. These glues are available in a series ofgrades, the higher grades gelling more quickly than the lower gradesunder similar conditions. Formulas have been developed to improvethe moisture resistance of animal glue, but their use is not recommendedfor amateurs. Hot animal glues, prepared by the user and used as soonas possible after melting, give best results. Control of wood and gluetemperatures and of assembly time, however, are critical with hot ani-mal glue. Liquid animal glues appear to vary considerably from sampleto sample.(5) There are a number of kinds and grades of casein glue. For gluingwood used in archery, a water-resistant or "joint" grade of casein glueshould be used. Casein glues are used cold. Because of their highalkalinity, these glues tend to stain woods containing extractives.(6) Urea-resin glues (one type of synthetic-resin glue) set at 70 F. orabove. They are generally available in local hardware and building sup-ply stores as powders to be mixed with water before use. These gluesare convenient to use, develop a high degree of water resistance, arecolorless, and do not stain the wood. Their rate of strength develop-ment can be increased by heating the joint. The glue mix will set hardand insoluble in water within a few hours, so that it cannot be cleanedaway or used after this hardening. The sensitivity of urea resins tolong exposure at elevated temperatures should not be a significant limita-tion for archery applications. Special gap-filling formulations of urearesins are preferred by some archers.(7) Resorcinol-resin glues are the most recent type of woodworking glue.These glues cure or harden at 70 F. or above, generally somewhatmore slowly than urea resins. They are available in liquid form to whicha separate powdered hardener is added before use. Resorcinol-resinglues produce a dark red or brown glue line, set hard within a few hours,and are the most durable of all room -temperature -setting woodworkingglues. Generally excellent, durable bonds should be possible when theyare properly used. At least one brand of resorcinol glue is availablein retail shops, but the cost is higher than that of other glues.(8) Various phenol-, melamine-, urea-, and other resin glues are avail-able that cure at 240 F. or higher, but these are not generally feasiblefor the amateur archer.(9) Polyvinyl-resin emulsion glues are supplied as liquids ready to useat room temperature. Since they lack the water resistance of casein

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glues and other resin glues and are subject to some slippage and flowin joints under load, they are not recommended for most wood-to-woodjoints in archery equipment. They may be very useful, however, forgluing leather, plastics, and other flexible materials to wood for trimwhere high stresses are not exerted on the joint and where their quicksetting and colorless glue lines are distinct advantages.(10) Nitrocellulose -.base cements (pyroxylin) are particularly useful forattaching feathers to arrow shafts, plastic nocks or points to arrowshafts, and leather grips or handles to bows. Nonaqueous cements ofthe hot-melt type, such as DeKhotinsky cements, are often preferredfor attaching metal points to shafts.(11) A number of new adhesive -bonding procedures have been developedin recent years for bonding metals and plastics to wood in conjunctionwith the manufacture of aircraft and other specialized equipment, butmany of these processes are still in the experimental stage and cannotbe easily adopted by the typical archery enthusiast at this time. Theywill offer, however, to the archer with a technical interest a variety ofopportunities to experiment with interesting new composite materials, z.Interest in such materials has increased because of the increasing short-age of the most desired species and quality of wood for bows.

Special Use Requirements

(1) For fishtail splices in staves and for footing joints in arrows, highstrength and water resistance are important. A good fit and a largerbearing surface affect dry strength more than the type of glue. In stavesthe bearing surface may be enlarged by keeping plenty of thickness underthe handle. In shafts a sufficient bearing surface is assured if the lengthof the splice is at least 15 times the diameter.(2) The choice of glue for attaching feathers to shafts depends on thedegree of water resistance desired and on the rate of gelling of the gluefor the particular mechanical method used for feather attachment. Ani-mal glues have been used, but nitrocellulose -base cements (pyroxylin)now seem to be preferred and appear to have acceptable moisture resist-ance. Glues of the woodworking types, known to be more moisture re-sistant, are not generally convenient to use for attaching feather s becauseof their slow hardening under normal conditions.The bonding of wood to metal is discussed in Forest Products Labora -

tory Report No. R1768.-3-


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(3) Glues for attaching bow backings and facings must produce bonds thathave high strength and high moisture and water resistance and that areable to bend with the bow without failure. Glue films applied to the woodfor laying sinew, silk, or high-tenacity rayon fibers as backings andfacings must bend without cracking. Animal and certain resinglues havebeen used for these purposes.

Gluing Properties of Archery Woods

Since a good glue joint is usually considered to be one that is strongerthan the wood being bonded, the stronger high-density species requirestronger bonds than the low-density woods. Therefore, more carefulcontrol of the gluing conditions is required to produce satisfactory jointsin hickory than in spruce or pine. Oily woods, such as yew, osage or-ange, or lemonwood, that are commonly favored for bow staves may bemore difficult to glue than woods of the same density but without oils,resins, or extractives. Oily woods may glue better when freshly ma-chined than later. Sponging oily wood surfaces with a 10 percent solu-tion of caustic soda, wiping off the excess, and drying before gluing oftenimproves gluability with animal and casein glues. Since residual alkaliis likely to interfere with the catalyst systems of many urea- andresor-cinol-resin glues, this alkali surface treatment should not be used withthese resin glues. Gluability with these resin glues may, however, beimproved by the use of somewhat elevated curing temperatures -- 100F. or so -- during the pressure period. Care must be taken to avoidexcessive drying of the wood during such curing of the glue.

UN1VERSITY OF-FLOmDA

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ZM38178F _4_ Agriculture-Madison

Glues for wood in archery uses (1952) -

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